Encoders and R&P machine

[bruce_clark]

Has anybody else added encoders to a rack and pinion
machine? I added some encoders to my r&p machine
and the software (sb2b10) seems to ignore them.

Now, I remember someone posting the command to
disable/enable the encoders. Could someone please
post that command again.

Thanks,
Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[birdsofplay]

I believe it was ...

VK ,,,,,,,-1, -1 for "ON"

or ...

VK ,,,,,,,0, 0 for " OFF"

[bruce_clark]

Another question about encoders. Since I am using
some 1000 line encoders, the SB software seems to
think this is still the 128 line encoders and so
the machine does not move the "right" distance. I
have tried a lot of stuff, but basically it boils
down to: How do I set the encoder resolution on
my SB?

BTW, thanks Bob. That was the correct command,
though undocumented.

Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[bruce_clark]

More questions...

Ted suggested that the control box was "missing"
steps because of the hi resolution, so I went
back to the Clarostat 128 line encoders with the
same gearing, 20T directly riding against the rack
(for 128 lines per inch of travel or 512 lpi in
quadrature). Ok, now I think everything is the
same EXCEPT the X axis now runs BACKWARDS and to
top it off, I cannot make it EVER go in a positive
direction!

I am up for suggestions. Does ANYBODY else out
there have encoders on a rack and pinion machine?

Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[donchandler]

Bruce,
It sounds like the encoder is out of phase with the motor. Try swapping the channels.
Have you been looking at the digital readout board from Dan Mauch? Sure would be nice to figure out how to interface it to the control box software.
BTW how are you doing with Vector? I am doing better with BobCad than I was. How did you set up your varibles in the cam section?

[bruce_clark]

Don,

Yea, I thought that too, but I think it is too
intermitten to be _only_ out of phase (though I
think that is a problem also).

As for Dan Mauch's board, I have ordered a 4 axis
version. I am hoping that the EMC project will
support that board (fingers crossed).

As for Vector, I am still using Bobcad 16.1, but I
downloaded version 17.0 and it looks pretty good.
Anyways, Fred Smith offered to upgrade me to
Vector for the same price as an upgrade to Bobcad
17.0 (this offer is good to ALL Bobcad 16.1 owners
til August 1st). So, I went ahead with Vector.

There is a new version of Vector coming out August
1st (or so) and Fred promissed much better ShopBot
support (no more converting arcs to line
segments), though personally, I still find it
easier to draw stuff Bobcad.

Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[densull@megsinet.net]

I'm wondering... Would it be practical to modify a Shopbot by adding a longer Z axis stroke assembly? I understand that it would need to be rigidized considerably. A longer screw would be needed, too, and perhaps even a different type of guide tracks.
I'm consulting with a client that needs an economical solution to machining thermoforming molds in wood, and the plastic parts to be formed are deep--up to two feet. Building the special table shouldn't be a big problem. It would just require a lower or perhaps adjustable working surface. The Bosch or PC router could be mounted on an indexing fixture so that it could be turned at fixed angles and the machine re-zeroed in order to reach near-vertical surfaces,(emulating a 4 axis router) using ball-nose cutters.

The next question: is the latest Shopbot software capable of 3-axis interpolation? In other words, can we machine 3d shapes with the new Shopbot?

Another question: I see in the price list the mention of a digitizing package (at a quite reasonable cost, by the way). How does this work?
Is it capable of 3d digitizing? (We manufacture large 5' x 12' digitizers, but we don't currently do 3d). Does the system track over the model to be scanned in small step increments and respond to probe input in the Z axis and write a file of points?
Just wondering if I can build up a Shopbot and use it for a 3d digitizer... Any ideas?

The Shopbot is a marvelous and versatile tool, and I would certainly have one myself, but I found the Shopbot too late--after I had already acquired an early Digital Tool kit router. We now have a model 903 with Z and W axes. It covers 5 feet by ten feet with about a seven inch vertical stroke. Digital Tool (DT Technologies)passed away last summer, but that's not a major problem--except for them, of course! Due to design problems and some really shabby manufacturing and assembly, I have had to rebuild and rework much of this machine in order to get the smooth operation and accuracy I want. I bought the kit version, and built my own welded steel base with about 1200 pounds of steel. It doesn't move around much!
I'm thinking about adding digital steppers to the X and Y axes in order to speed up the rapid moves to nearly 1000 IPM.

Dennis Sullivan Skalar Systems

[Ted Hall, ShopBot]

Hi Dennis,

Thanks for all the good questions. Let me see if I can address them:

1. Long Z Axis. We have extended the Z axis for several customers. As you note, the problem becomes one of stiffness as the lever angle increases with increased cantilevering of the cutting head. If you give us a call, we can probably give you some more task-specific suggestions and information about the feasibility of this modification.

2. Three-D Interpolation. Yes, ... full 3 D movement in X,Y and Z. You can also software-switch the 4th axis so that it can optionally be the Z axis in a 3D move.

3. Yes, we do sell a digitizer that functions as you describe. There's a simple sample version of the current software to operate it (or a probe of your own design) in our current beta software which you can download here. Have a look at the Part file (S_ProbeV3.SBP) and you'll get the idea. [If you probe a metal object with a paper clip, this system is essentially free.]

Let us know if you have other questions.

[densull@megsinet.net]

Thanks, Ted!

I recommended that my clients visit the Shopbot website, and investigate building a special version. They'll be visiting our shop, so I'll pass along the information on the long Z axis to them.
An alternative to machining the wood molds in one tall piece would be to "slice" the CAD model into manageable 4 to 5 inch high sections, program and cut them and assemble them on the bench. A Shopbot would work for that approach, too.

Best Wishes,

Dennis Sullivan